The present invention relates to a gas turbine in which moving blades are cooled and, more particularly, to a gas turbine of closed cooling type in which coolant for cooling moving blades is recovered.
Further, the present invention relates to a gas turbine in which thermal stress is relaxed by heating an axis portion of a rotor shaft at a starting time.
In JP A 3-275946, concerning gas turbines having flow passages for supply/recovery of coolant to/from moving blades arranged inside discs and spacers forming a rotor, a gas turbine is disclosed which is provided with solid discs having no central hole at a center thereof (a shaft center).
Metal temperature distribution of a rotor and thermal stress and thermal deformation applied on the rotor are affected by the heat from and to spaces inside the rotor and a peripheral surface of the rotor, etc.
On the other hand, in JP A 3-275946 any concrete measures are not taken for the above-mentioned heat affection.
During unsteady operation at a starting time, the temperature rises largely in the rotor peripheral portion by the heat inputted from a working gas of the gas turbine, while it is not easy for the central portion of the rotor to be warmed.
Further, in the case where a supply path and a recovery path for a blade cooling coolant are provided, thermal stress in the rotor of gas turbine of closed cooling type becomes large because a temperature difference corresponding to a temperature increment due to cooling of the moving blades occurs between the supply path and the recovery path, so that there is a fear that a large stress is applied on the rotor central portion by overlapping of the thermal stress applied on the rotor discs, etc. and centrifugal force caused by rotation.
Therefore, an object of the present invention is to provide a gas turbine in which operational reliability thereof is improved by suppressing thermal stress applied on a rotor central portion.
A first feature of the present invention resides in a gas turbine having a rotor shaft constructed by arranging, in an axial direction in turn, a plurality of discs each having a plurality of combustion gas-driven moving blades annularly arranged on the peripheral portion and spacers arranged between the discs, and is characterized in that the above-mentioned discs each are formed in solid disc, gap portions are formed between a region, on the rotor shaft center portion side, of the above-mentioned discs facing the spacers and spacers adjacent thereto, contact surfaces are formed both of which contact on both a region, on the rotor peripheral side, of the above-mentioned discs facing the spacers and adjacent spacers thereto, and a third flow path leading fluid to the above-mentioned gap portions is provided.
Thereby, it is possible to control heat flow from and to the rotor members, to reduce thermal stress applied on the rotor members and to improve reliability of the rotor members at a time of starting.
A second feature of the present invention resides in a gas turbine having a rotor shaft constructed by arranging, in an axial direction in turn, a plurality of discs each having a plurality of combustion gas-driven moving blades annularly arranged on the peripheral portion and spacers arranged between the discs, the above-mentioned moving blades having flow path introducing coolant for cooling the moving blades and discharging out the coolant heated by the combustion gas, and is characterized in that contact surfaces are formed both of which contact on both a region, on the rotor peripheral side, of the above-mentioned discs facing the spacers and adjacent spacers thereto, and a supply path, for supplying the above-mentioned coolant for cooling the moving blades, passing through the above-mentioned discs and spacers in the region forming the above-mentioned contact surfaces in an axial direction of the rotor and a recovery path for the coolant heated through the moving blades are provided.
As constructional flow paths of supply flow path and recovery flow path, a supply flow path and a recovery flow path for coolant are provided which pass through discs or spacers in the axial direction from inside the contact surfaces of the discs and discs or of the discs and spacers, the discs and spacers are separated from each other by the contact surfaces, whereby it is unnecessary to provide attachments such as separation pipes, connection pipes for separation of the flow paths, so that there is no fear that the attachments fall down and are broken and reliability is raised.